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Optics is the study of light, and its interaction with matter. It includes topics such as imaging systems, fiber optics, lasers, quantum optics, and more.

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Material that becomes visible when under water

Is there any preferably invisible material or paint that starts glowing or changing color under the water of any temperature (under or equal to 100 degrees celsius) without affecting the water ...
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2answers
20 views

What is the optimal light setting for human vision? In other words, is my vision better during the day or at night?

There seems to me to be two main effects that should be considered in answering this question. The first is that the iris dilates in low-light settings, which causes an increase in the numerical ...
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10 views

Finding youtube channel and tutorials which help me to revise the topics of seniour secandry classes [on hold]

I want to get any youtube channels or any other tutorial sites from where i revise my topics on magnetic effects of current,electromagnetic induction etc and many other topics.Can anybody provide me ...
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30 views

A geometrical calculation in Fresnel's paper “Memoir on the diffraction of light” 1819

It is a geometrical problem which I find difficult to solve reading the Fresnel's paper "Memoir on the diffraction of Light". According to the figure Fresnel sets $z$ as the distance of the element $...
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2answers
39 views

Why do lights appear like straight lines on a windshield of a car? (becomes more prominent at sunset and night)

i think thats the Diffraction of light caused by the scratches in the glass. or the wiper blade leave a pattern of dirt and grime in an arc. i hope someone can confirm my logic. my seconde question ...
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21 views

Displacement of image due to displacement of object and mirror [on hold]

I don't know how to solve it so please solve my optics problem
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26 views

Computation of refractive index of the upper atmospheric air using pressure, temperature and humidity measurements

Upper Air Sounding Systems (UASS) measure the properties of the atmosphere typically till a vertical height of 30 km from Mean Sea Level (MSL). The balloon-suspended sensors used over here measure ...
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1answer
43 views

Why must the converging lens have a shorter focal length than the diverging lens if the latter focal length is to be determined by combining them

Why must the converging lens have a shorter focal length than the diverging lens if the latter focal length is to be determined by combining them? When we had done the experiment in lab we did ...
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1answer
87 views

Why do I see discrete images when moving an object in front of a screen?

I observed this while doing my homework. I have a habit of shaking my pen between my fingers vigorously while thinking something. My PC's screen is right in front of me (on my study table itself). ...
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17 views

Calculation of single photon detector sensitivity versus integration time

How does sensitivity scale with integration time for the minimum detectable signal in single photon counting experiments (SNSPD)--- how to factor in noise/jitter etc and which noise can not be ...
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1answer
29 views

Principle of reversibility of light in case of refraction at the critical angle

In the case where light is moving from denser medium to a rarer medium, at the critical angle, the refracted ray will be parallel to the surface. Now according to the principle of reversibility of ...
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1answer
48 views

Does focal length change when curbe mirror is dipped in liquid? [on hold]

In a physical optics chapter, I found this question: Does the focal length change when a curve mirror is dipped into liquid? Please explain it and help me understand.
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1answer
47 views

What is the optical effect on this video? [on hold]

People seem transparent in that video. What does explain that? https://www.instagram.com/p/BmJDU1Snd1O/?utm_source=ig_share_sheet&igshid=1qwkhrbxglb3q
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1answer
70 views

Superior Mirage

I've been fascinated about mirages and never thought I'd get to see a superior mirage. I live on the south coast of England and enjoy a distant view of the English channel. Last Friday 3 August 2018 ...
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0answers
24 views

Do the laws of geometric optics only apply to linear media?

Do the laws of geometric optics, the incident, reflected and transmitted rays lie on the same plane; $\theta_r = \theta_i$; $n_i \sin\theta_i = n_t \sin\theta_t$ (Snell's law), apply only when ...
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15 views

Clarify an assertion about refracted and reflected waves in Feynman

In The Feynman Lectures vol. 1, chp. 33, Feynman is disucssing about intensity of light and says that: The principle that we must understand is as follows. The currents that are generated in the ...
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1answer
42 views

Can visible light be composed of invisible electromagnetic frequencies?

I know that when we see red light (via electromagnetic frequencies in the red range) and blue light (via electromagnetic frequencies in the blue range) at the same time, we perceive it as magenta ...
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2answers
76 views

Path difference in double slit experiment

Generally the path difference between two rays is considered as dsin$\theta and for this generally the two rays are considered parallel. That is shown in diagram 'c'. My questions - 1. is even ...
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42 views

Effects of lenses

I have three convex lenses that I'm arranging so as to function as a crude magnification device. My question is about the image that I see. It seems that no matter how I arrange them, with respect to ...
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0answers
26 views

Too Low Visibility of Interferometric Autocorrelation data

I've done interferometric autocorrelation experiment by KMLabs femto-second laser. center peak of pulse laser is 777 nm & FWHM is 40 nm. I check it by spectrometer. and using BBO crystal(0.7 mm)...
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2answers
85 views

Why does shorter focal length result in greater beam divergence?

So I got 2 converging Fresnel lenses, one with 50 mm focal length and other 70 mm. My experiment looks like this: When trying to focus and SMD LED emitter into a narrow beam (sticking to lenses ...
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2answers
70 views

Contradiction on the behavior of refractive index

The refractive index is given by: $$ n = \sqrt{\mu_r \epsilon_r} $$ This equation is symmetric about wavelength and is same for all wavelength of light i.e. since $\mu_r$ and $\epsilon_r$ are ...
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1answer
33 views

How do CRA (Chief Ray Angle) and FOV (Field of View) affect one another?

I've been researching CMOS image sensors for a small working-distance, low-light application. From this, I roughly know I need a field of view of approximately 100-120 degrees. However, upon looking ...
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1answer
23 views

Best glass to reflect visible light (mainly Green)

i have a laser source which emits green light underwater (kept collimator under water) and planning to reflect the green laser back to free space(project is to establish air water interface). I want ...
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1answer
25 views

Data in Optical Fiber Communication?

Data is transferred in the form of light signals in an optical fiber. More will be the light signals/beams in a single strand at a time means more will be the data in that strand or a single strand of ...
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2answers
34 views

Why is Copper (I) Oxide Red?

This may appear to be a chemistry problem; but, after reading the Wikipedia article on Copper (I) Oxide, it seems to have more to do with semiconductor-physics. For example: "...light travels almost ...
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1answer
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Why do I see red light reflecting from my normal glasses when I wear anti blue-ray glasses?

Today when I went for eye checkup, the optician presented to me an anti blue ray glasses. This type of glasses reflect blue light, and hence, while wearing my original glasses and holding this new ...
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2answers
58 views

How do our eyes restructure the picture of objects “right side up”? [closed]

I hope I am posting this in the correct site. I am puzzled with the following sentence: Time and space are compressed into a point of no dimension through which images of the things around us are ...
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1answer
50 views

Mach-Zehnder interferometer reaction to input light with polarization state ±45˚?

We have a Mach-Zehnder interferometer with two non-polarizing beam splitters. The polarisation state of the input beam is a superposition of +45˚ and -45˚ polarizations. In the upper arm of the ...
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2answers
85 views

Why does Fermat's principle (optics) not apply to all paths?

Feynman's statement of Fermat's Principle regarding optics is the following, "a ray going in a certain particular path has the property that if we make a small change (say a one percent shift) in ...
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1answer
49 views

Why is fused silica superior to N-BK7 in terms of thermal lensing?

In optics lab, the two commonly used types of glasses are N-BK7 and fused silica. The lab wisdom has been that fused silica is superior to N-BK7 in terms of thermal lensing. And indeed it seems so. ...
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2answers
91 views

Why cannot we see too small objects with naked eyes?

Why is there a lower limit to the size of objects we can see with our naked eyes? What are the factors at work; diffraction, light reflected, resolution of eyes?
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58 views

Fabry-Perot cavity modelling

I'm trying to understand the modelling used for Fabry-Perot cavities, such as it is done in e.g. this paper: http://aip.scitation.org/doi/10.1063/1.1729109 The model given is based on the following ...
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1answer
76 views

Newton's ring conceptual doubt

Newton’s rings are formed as a result of interference between light waves reflected from the upper and lower surfaces of the air film developed between the convex surface of the plano-convex lens and ...
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1answer
27 views

How to evaluate LED illuminance based on luminous flux and directivity / radiation pattern?

I am building an LED-light and am trying to figure out how many LEDs I need to be on it. I know how much illuminance I need as well as the distance to the subject and the luminous flux of one of the ...
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0answers
70 views

How to amplify a light source while preserving its wavelength?

If I have a monochromatic light source of wavelength λ, that is quite feeble, say 1nW, is there an equipment that will let me amplify this signal with an output at precisely the same wavelength?
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21 views

resulting refractive index of multiple layers with different indexes

I am wondering whether my chain of thought is right because this seems very counterintuitive to me. But I calculated that if I have multiple layers with different refractive indexes stacked onto ...
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1answer
50 views

Why are powdered silver and powdered platinum black?

The quantum-mechanical (relativistic) explanations for the observed colours of copper, silver & gold don't appear to explain the black colours of powdered silver (& powdered platinum). Can ...
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38 views

How do we proof that parallel light rays(which are not parallel of principal axis) meet at focal plane?

Parallel rays coming from infinity are said to meet at focal plane.I was looking for the proof of that phenomena
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41 views

Does the optical density of a medium depend upon its mass density?

The optical density of a medium is quantified by its refractive index $n$. Does it have any correlation with the mass/number density of the medium? In other words is an optically denser medium must ...
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56 views

Is light visible? [closed]

I was confused when i saw the rgb spectrum where the light goes on a prism and then we get the colours .. we see the source of the refracted light ? like seeing a blue sun ?
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3answers
45 views

How light help us see objects?

For example imagine we have an object in an area with wind...how the reflected light come to our eyes and doesnt travels with air (medium) ? also can the light be reflected in all directions so every ...
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1answer
20 views

Cube Beam Splitter Ratios in Reverse

Good day to all, I the following diagram is a non-polarized beam splitter cube with a 10:90 (R:T) split ratio. The questions I have are: that when light comes back does the 90°, R path still have a ...
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2answers
107 views

Can you burn invisible jelly balls with a laser?

Suppose you have some jelly balls with similar refractive index as that of water, like in this video. You put them in water, making it invisible. So, the optical behavior of the balls should be ...
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40 views

Making two laser colinear

Are there any known configuration that would allow me to make two laser beam colinear? Currently this is my configuration that allows me to use one of the laser. I can't seen to find a configuration ...
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1answer
43 views

Silver telescope mirror restoration

Our physics department has recently acquired a 26 inch diameter silver telescope mirror that is quite a bit tarnished. Would attempting a light bit of polish be possible before we try to resurface ...
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0answers
16 views

Effect of Quantum Efficiency of a CCD on the intensity and how to normalize it?

I have a multi spectral with around 25 bands in the near IR range i.e there are 25 different wavelengths that the CCD can capture. For each of these CCD filters the Quantum Efficiency curves differ ...
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28 views

Different fiber coupling efficiency for two single-mode fibers with the same core diameter

Hi Physics StackExchange community, Today I had to re-do the entire optical path for the delivery of a 830 nm laser from our laser table to the experiment table. For the fiber coupling, I usually use ...
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21 views

Is the object focus always on the same side as the incident ray in converging lens?

We know that representation of a lens is made up of the lens itself, the principle axis, 2 foci points (object and image focus) and the optical center. In my notes it says that in a converging lens ...
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1answer
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Optical scattering Vs size of wavelength

I am having trouble understanding the my slide was given in my lectures in intro to optics. The reason when why I am having trouble is because when I went to research more about each scattering, I ...